CN106935970B

CN106935970B - Metamaterial structure, radome, antenna system and method for forming sandwich structure

Info

Publication number: CN106935970B
Application number: CN201511032164.3A
Authority: CN
Inventors: 不公告发明人
Original assignee: Kuang Chi Institute of Advanced Technology
Current assignee: Kuang Chi Institute of Advanced Technology
Priority date: 2015-12-31
Filing date: 2015-12-31
Publication date: 2021-09-03
Anticipated expiration: 2035-12-31
Also published as: WO2017114131A1; CN106935970A

Abstract

Metamaterial structures are disclosed, as well as radomes and antenna systems incorporating metamaterial structures. The metamaterial structure includes: a first dielectric substrate; and a plurality of conductive geometries on the first dielectric substrate, wherein each conductive geometry is a centrosymmetric distribution pattern and adjacent conductive geometries are spaced apart from each other. The change in the shape and size of the conductive geometry results in a change in the electromagnetic wave response characteristics. The antenna housing can improve the wave transmission performance of electromagnetic waves in a working frequency band, and can be used as a filter to inhibit the penetration of the electromagnetic waves in a non-working frequency band, so that the signal-to-noise ratio of the antenna in working can be improved.

Description

Metamaterial structure, radome, antenna system and method for forming sandwich structure

Technical Field

The present invention relates to a radome, and more particularly, to a metamaterial structure, and a radome and an antenna system including the metamaterial structure.

Background

The antenna system typically includes a radome. The antenna housing aims to protect the antenna from being influenced by wind, rain, ice, snow, dust, solar radiation and the like, so that the working performance of an antenna system is stable and reliable. Meanwhile, the antenna housing can reduce abrasion, corrosion and aging of an antenna system, and the service life is prolonged. However, the radome is an obstacle in front of the antenna, and absorbs and reflects the radiated wave of the antenna, so that the free space energy distribution of the antenna is changed, and the electrical performance of the antenna is influenced to a certain extent.

The radome should have a certain mechanical strength to protect the internal antenna, and should allow the electromagnetic waves in the operating band to efficiently penetrate through to reach the internal antenna. The existing antenna housing is basically a pure material antenna housing, and mainly plays a role in protecting the antenna. In order to improve the efficient penetration of electromagnetic waves, the material thickness can be designed by adopting a half-wavelength theory. When the thickness of the material of the antenna cover is 1/2 of the wavelength of the electromagnetic wave in the working frequency band, the penetration rate of the electromagnetic wave is best. Therefore, the thickness design of the pure material radome depends on the wavelength of the electromagnetic wave in the operating frequency band. As the wavelength of the electromagnetic wave in the operating band increases, the thickness of the radome should also increase. The weight of the radome may increase to a level where it is difficult to apply. On the other hand, the common material has uniform wave-transmitting performance, wave-transmitting in the working frequency band and excellent wave-transmitting effect of the adjacent frequency band, and the wave-transmitting outside the working frequency band is easy to interfere with the normal work of the antenna.

At present, materials for preparing the antenna housing mostly adopt materials with low dielectric constant, low loss tangent and high mechanical strength, such as glass fiber reinforced plastics, epoxy resin, high molecular polymer and the like. The structure of the antenna housing is mostly an even single-wall structure, an interlayer structure, a space skeleton structure and the like. Due to the fact that the design of the thickness of the radome wall needs to take the working wavelength, the size and the shape of the radome, the environmental conditions, the performance of the used materials in the aspects of electricity and structure and the like into consideration, the wave-transmitting performance is possibly poor, and the working frequency band is narrow. The antenna housing needs to be replaced aiming at different frequency bands, so that resource waste and equipment cost improvement are caused.

Disclosure of Invention

The invention aims to provide a broadband wave-transmitting structure capable of improving wave-transmitting performance.

The technical problem to be solved by the present invention is to provide a metamaterial structure, and an antenna cover and an antenna system including the metamaterial structure, aiming at the above-mentioned defects of poor wave-transparent performance and narrow working frequency band in the prior art.

According to an aspect of the invention, there is provided a metamaterial structure comprising: a first dielectric substrate; and a plurality of conductive geometries on the first dielectric substrate, wherein each conductive geometry is a centrosymmetric distribution pattern and adjacent conductive geometries are spaced apart from each other.

Preferably, the centrosymmetric distribution pattern is at least one pattern selected from a square shape, an i-shape, a snowflake shape and a field shape.

Preferably, the conductive geometry is a checkerboard pattern comprising: the square outer frame is composed of four side edges, and the outer frame is provided with a first length, a first width and a first line width; the first line is connected with a group of two opposite side edges and has a second line width; and a second line connecting the other set of two opposite sides, the second line having a third line width; wherein the conductive geometry is shaped and dimensioned to achieve a desired electromagnetic wave response characteristic.

Preferably, the first line connects midpoints of the groups with respect to both sides.

Preferably, the second line connects midpoints of two opposite sides of the other group.

Preferably, the first length is not equal to the first width to match the polarization direction of the antenna.

Preferably, the second line width is not equal to the third line width to match the polarization direction of the antenna.

Preferably, the first line width is not equal to the second line width and the third line width, so as to adjust the steepness of the cut-off waveform of the electromagnetic wave response curve.

Preferably, the material form of the conductive geometry is one selected from the group consisting of solid, liquid, fluid and powder.

Preferably, the electrically conductive geometry is comprised of a liquid, electrically conductive material and is contained in one of the cavity, the tube and the capsule to define a shape thereof.

Preferably, the first dielectric substrate is composed of a material having a relative dielectric constant of more than 2 and a loss tangent of less than 0.1.

According to another aspect of the present invention, there is provided a radome comprising: the metamaterial structure described above; and a second dielectric substrate on the first dielectric substrate, wherein the plurality of conductive geometries are sandwiched between the first dielectric substrate and the second dielectric substrate.

Preferably, the first dielectric substrate and the second dielectric substrate are flat.

Preferably, the first dielectric substrate and the second dielectric substrate are curved, and the plurality of structural units are conformally formed on the first surface of the first dielectric substrate.

Preferably, at least one of the shape and size of the structural unit in the different regions of the radome is set according to at least one of wave-transmitting performance and filtering performance.

According to another aspect of the present invention, an antenna system is provided, which is characterized by comprising an antenna and the antenna housing, wherein the antenna housing is arranged on the antenna.

The antenna housing provided by the embodiment of the invention has high transmittance of electromagnetic waves in the working frequency band of 0-1.5 GHz. The radome may be acted upon by solid air, passing electromagnetic waves through the radome from the exterior of the radome to the interior antenna. Outside the operating frequency band, the reflection or attenuation of electromagnetic waves is significant, making it difficult to pass through the radome from outside the radome to the inside antenna. The antenna housing not only can play a role in wave transmission, but also can play a role in a filter, so that the signal-to-noise ratio of the antenna during operation is improved. By adjusting the shape and size of the conductive geometric structure, the polarization of the antenna can be matched, so that the transmission of incident electromagnetic waves in a selected polarization direction can be allowed to the maximum extent, and the signal-to-noise ratio of the antenna is further improved.

The antenna cover provided by the embodiment of the invention can realize impedance matching with air, so that the transmission of incident electromagnetic waves is increased to the maximum extent, and the limitation on the thickness and the dielectric constant of materials in the design of the traditional antenna cover is reduced. According to the antenna system provided by the embodiment of the invention, after the antenna housing is added on the antenna, the radiation capability of the antenna is enhanced, and the gain is effectively improved.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic diagram of a building block of a metamaterial structure according to an embodiment of the invention;

fig. 2 shows a schematic structural view of a radome according to an embodiment of the invention;

fig. 3 shows a schematic simulation diagram of S-parameters of a radome according to an embodiment of the invention.

Detailed Description

The invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by like reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale. In addition, certain well known components may not be shown.

It will be understood that when a layer or region is referred to as being "on" or "over" another layer or region in describing a structure, it can be directly on the other layer or region or intervening layers or regions may also be present. And, if the structure is turned over, the layer, region or regions will be "under" or "beneath" another layer, region or regions. If for the purpose of describing the situation directly above another layer, another region, the expression "a directly above B" or "a above and adjacent to B" will be used herein.

The present invention may be embodied in various forms, some examples of which are described below.

Fig. 1 shows a schematic view of a building block of a metamaterial structure according to an embodiment of the invention. In fig. 1, a structural unit 100 is shown, which comprises a conductive geometry 110. The length and width of the structural unit 100 are denoted as a and B, respectively. The conductive geometries 110 are located within the structural unit 100 and are symmetrically distributed with respect to the center of the structural unit 100, forming a centrosymmetrically distributed pattern. The centrosymmetric distribution pattern is one selected from a square, an I-shaped, a snowflake and a Chinese character tian. In one example, the pattern of conductive geometry 110 is a checkered pattern including a square-shaped outline 111, a first line 112, and a second line 113. The first and

second lines

112 and 113 are respectively connected to midpoints of opposite sides of the outer frame 111 to cross each other. The length and width of the outer frame 111 are denoted as a and b, respectively, and are parallel to the length and width directions of the structural unit 100, respectively, and are slightly smaller in size. The line width of the outer frame 111 is W1, the line width of the first line 112 is W2, and the line width of the second line 113 is W3.

In the structural unit 100, the length a and the width B of the structural unit 100, and at least one of the length a and the width B of the outer frame 111, the line width W1 of the outer frame, the line width W2 of the first line 112, and the line width W3 of the second line 113 may be changed according to different requirements for the regulating action of light or electromagnetic waves. If the length-width ratio a/b of the outer frame 111 is changed or the line width ratio W2/W3 of the first line 112 and the second line 113 is changed, the polarization characteristics of the radome can be adjusted to meet the requirements of different polarization directions of the antenna. If the line width ratio W1/W2 or W1/W3 of the outer frame 111 to the first and

second lines

112 and 113 is changed, the high frequency response characteristic of the radome, for example, the steepness of cutoff can be changed. The magnitude of the cut-off frequency can be changed if the size of the structural unit 100 is changed. For example, the larger the size of the structural element 100, the lower the cut-off frequency.

The conductive geometry 110 may be composed of any conductive material. The conductive material may be a metal material having good conductivity, such as gold, silver, copper, or the like, or an alloy material having one or two of gold, silver, and copper as a main component, or a conductive non-metal material, such as carbon nanotube, aluminum-doped zinc oxide, and indium tin oxide. In the present invention, the material of the conductive geometry 110 is preferably copper or silver. The conductive geometry 110 may be in any physical form. The form of the substance may be one selected from the group consisting of a solid, a liquid, a fluid and a powder, as long as the substance can maintain a specific shape. The electrically conductive material, e.g. a liquid, may be contained within and define the shape of the cavity, tube, capsule.

Although not shown in the figures, the conductive geometry 110 may be formed on a dielectric substrate. There are many choices of materials for making the dielectric substrate, such as ceramic, FR4, F4B (polytetrafluoroethylene), HDPE (High Density Polyethylene), abs (acrylonitrile Butadiene styrene), etc. For example, the dielectric substrate has a relative dielectric constant of more than 2 and a loss tangent of less than 0.1. The conductive geometry 110 may be attached to the dielectric substrate by printing, plating, adhesive bonding, hot pressing, and the like.

In one example, the conductive geometry 110 is a patterned metal layer on a dielectric substrate. The conductive geometry 110 is attached to the dielectric substrate by a variety of methods including etching, plating, drilling, photolithography, electrolithography, or ion lithography. The etching process is a preferred process, and includes the steps of after designing a plane pattern of a suitable artificial microstructure, integrally attaching a metal foil to a dielectric substrate, removing the foil part except the preset pattern of the artificial microstructure by chemical reaction of a solvent and metal through etching equipment, and obtaining the artificial microstructure from the rest. In another example, the conductive geometry 110 may be formed on the dielectric substrate by printing with a conductive ink.

Fig. 2 shows a schematic structural diagram of a radome according to an embodiment of the present invention. A plurality of structural units 100 are located between the first dielectric substrate 200 and the second dielectric substrate 300, forming a sandwich structure. In the plurality of structural units 100, the conductive geometries of adjacent structural units 100 are spaced apart from one another, i.e., the checkered patterns of structural units 100 are spaced apart from one another without touching one another.

The radome is not limited to a flat plate shape but may be provided in any suitable shape depending on the shape of the antenna and the requirements of the application. For example, when the radome is applied to an airplane, the radome has a curved shape. Accordingly, the first and second

dielectric substrates

200 and 300 should also have a curved surface shape. The plurality of structural units 100 are conformally formed on the surface of the first dielectric substrate 200.

In various embodiments of the present invention, the conductive geometry in different structural units 100 is a checkerboard, and a plurality of structural units 100 are arranged in an array in rows and columns, and the centrosymmetric pattern of each structural unit 100 is the same. The arrangement of the structural elements, the shape and the dimensions of the conductive geometry may be the same or different in different areas of the radome, depending on the antenna type and the requirements of the application. For example, in order to adapt the polarization direction of the antenna, the aspect ratio a/b of the outer frame of the conductive geometry is different and/or the line width ratio W2/W3 of the first and second lines is different in different areas of the radome. In order to improve the wave-transparent properties of the radome, for example to obtain a broadband wave-transparent, the dimensions of the outer frame of the conductive geometry may be different in different areas of the radome.

Thus, in an alternative embodiment, the plurality of structural units 100 are arranged in an array in rows and columns, and the centrosymmetric patterns of the plurality of structural units 100 in adjacent rows may be different from each other. In another alternative embodiment, a plurality of structural elements 100 may be arranged in a plurality of concentric rings, with the same centrosymmetric pattern for each structural element 100. In another alternative embodiment, the centrosymmetric patterns of the plurality of structural units 100 of adjacent rings of the plurality of concentric rings may be different from each other. The different centrosymmetric patterns differ in at least one of pattern shape, pattern size, and line width.

The method of forming the sandwich structure includes forming a plurality of structural units 100 on one surface of a first dielectric substrate 200, and then adhesively fixing a second dielectric substrate 300 to the first dielectric substrate 200 to cover the first dielectric substrate 200 and the plurality of structural units 100 on the surface thereof.

Fig. 3 shows a schematic simulation diagram of S-parameters of a radome according to an embodiment of the invention. In the S-parameter simulation, it is assumed that the first dielectric substrate 200 and the second dielectric substrate 300 are composed of a material having a relative dielectric constant of 3.15 and a loss tangent of 0.008. The first dielectric substrate 200 and the second dielectric substrate 300 are flat plates, and the thickness thereof is 1.1 mm. In each area of the radome, the structural units have the same size, and the conductive geometric structure is composed of a square outer frame with the same line width, a first line and a second line. Specifically, the length a and the width B of the structural unit are both 6 mm, the length a and the width B of the outer frame of the conductive geometric structure are both 5.4 mm, and the line width W1 of the outer frame, the line width W2 of the first line, and the line width W3 of the second line are all 0.3 mm. The material of the conductive geometry was Ag and the thickness was 0.018 mm.

The simulation result of the antenna housing with the parameters shows that the S21 wave-transmitting rate of the antenna housing is close to 0dB in the frequency band of 0-1.5GHz, and the transmittance is high, so that the antenna housing can be used as a wave-transmitting structure to meet the application requirement of the antenna housing. The S21 wave-transmitting rate is less than-10 dB in the frequency band of 6.5GHz-12GHz, and the reflectivity is correspondingly high, so that the radar stealth structure can be used as the radar stealth structure to meet the application requirements of stealth structure materials. The wavelength selectivity characteristic shown in fig. 3 is advantageous in the application of the radome, the transmittance of the electromagnetic wave is high in the operating frequency band of 0-1.5GHz, the electromagnetic wave can pass through the radome from the outside of the radome to reach the antenna inside, and the reflection or attenuation of the electromagnetic wave is obvious outside the operating frequency band, so that the electromagnetic wave is difficult to pass through the radome from the outside of the radome to reach the antenna inside. The antenna housing not only can play a role in wave transmission, but also can play a role in a filter, so that the signal-to-noise ratio of the antenna during operation is improved.

As described above, the conductive geometry modulates light or electromagnetic waves according to the material of the dielectric substrate and the size of the conductive geometry. In different working frequency bands, the sandwich structure containing the conductive geometric structure can absorb electromagnetic waves so as to be used as a wave-transparent structure, or the sandwich structure can deflect or even reflect the propagation direction of the electromagnetic waves so as to be used as a stealth structure.

According to the invention, different conductive geometric structures are designed on the substrate, and the dielectric constant of each space point is changed through the electromagnetic response characteristics of the related metal layers, so that the electromagnetic response characteristics of the substrate to the working frequency band are similar to that of air. Therefore, attenuation of the microwave system caused by mismatching of characteristic impedance after the traditional medium is introduced is reduced, reflection is reduced, and transmission efficiency is improved.

The metamaterial structure may also be a multi-layer substrate, for example, including 3 layers of substrates, and the conductive geometric structures arranged as described above are disposed between adjacent substrates. And high wave-transmitting effect can be achieved. This property can be used in applications where special requirements are placed on the passage and blocking of electromagnetic waves.

Therefore, the invention also provides an antenna housing which is made of the wave-transmitting material and is used for being covered on an antenna, so that the antenna can be protected, the normal operation of the antenna in a working frequency band can be ensured, irrelevant frequency bands can be shielded, and interference can be eliminated.

It should be noted that the shape of the radome may be a flat plate with the same shape as the shape of the wave-transmitting material in the drawings, and the shape of the radome may also be designed according to actual requirements, for example, the radome is designed into a spherical shape or a shape (conformal radome) matched with the shape of the antenna, and the use of a plurality of flat plate structures spliced into a required shape is not excluded, which is not limited by the present invention.

The invention also provides an antenna system, which comprises an antenna and the antenna housing as described above, wherein the antenna housing is covered on the antenna. The antenna includes a radiation source, a feeding unit, etc., and the specific structure can be referred to the related art, which is not limited by the invention. The antenna body may be, for example, but not limited to, a panel antenna, a microwave antenna, a radar antenna, or the like.

The conductive geometric structure, the antenna housing comprising the conductive geometric structure, the antenna system and the antenna system have high wave transmission efficiency in a working frequency band, and can shield other frequency bands, so that interference is eliminated, and a good working environment of the antenna is ensured. After the antenna housing is arranged on the antenna, the radiation capability of the antenna is enhanced, and the gain is effectively improved. In practical application, by adjusting the shape and size of the conductive geometric structure, the relative dielectric constant, refractive index and impedance of the material can be changed, so that the pass band moves to high frequency or low frequency, or the bandwidth is changed.

In the above description, well-known structural elements and steps are not described in detail. It should be understood by those skilled in the art that the corresponding structural elements and steps may be implemented by various technical means. In addition, in order to form the same structural elements, those skilled in the art may also design a method which is not exactly the same as the above-described method. In addition, although the embodiments are described separately above, this does not mean that the measures in the embodiments cannot be used in advantageous combination.

The embodiments of the present invention have been described above. However, these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The scope of the invention is defined by the appended claims and equivalents thereof. Various alternatives and modifications can be devised by those skilled in the art without departing from the scope of the invention, and these alternatives and modifications are intended to fall within the scope of the invention.

Claims

1. A method of forming a sandwich structure comprising:

forming a plurality of structural units on one surface of a first dielectric substrate; then, the second dielectric substrate is fixedly bonded to the first dielectric substrate so as to cover the first dielectric substrate and the plurality of structural units on the surface of the first dielectric substrate;

wherein a plurality of conductive geometries are located within the plurality of structural units, respectively,

wherein each conductive geometry is a centrosymmetric distribution pattern and adjacent conductive geometries are spaced apart from each other; the conductive geometry is a checkerboard pattern, comprising:

the square outer frame is composed of four side edges, and the outer frame is provided with a first length, a first width and a first line width;

the first line is connected with a group of two opposite side edges and has a second line width; and

a second line connecting the other set of two opposite side edges, the second line having a third line width; wherein the conductive geometry is shaped and dimensioned to achieve a desired electromagnetic wave response characteristic;

the aspect ratio a/b of the outer frame or the line width ratio W2/W3 of the first lines to the second lines is changed to adjust polarization characteristics of a radome to which the method of forming a sandwich structure is applied; or the line width ratio of the outer frame to the first and second lines W1/W2 or W1/W3 is changed to adjust the high frequency response characteristic of the radome to which the method of forming the sandwich structure is applied.

2. The method of forming a sandwich structure according to claim 1, characterized in that:

the size of the structural unit is changed to change the size of the cutoff frequency.

3. The method of forming a sandwich structure of claim 2, wherein the first line connects midpoints of the set with respect to both side edges.

4. The method of forming a sandwich structure of claim 2, wherein the second line connects midpoints of the other set of opposing sides.

5. The method of forming a sandwich structure of claim 2 wherein the first length is not equal to the first width to match a polarization direction of the antenna.

6. The method of forming a sandwich structure of claim 2 wherein the second line width is not equal to the third line width to match a polarization direction of the antenna.

7. The method for forming a sandwich structure according to claim 2, wherein the first line width is not equal to the second line width and the third line width to adjust a steepness of a cutoff waveform of an electromagnetic wave response curve.

8. The method of forming a sandwich structure according to claim 1, wherein the material form of the conductive geometry is one selected from the group consisting of solid, liquid, fluid, and powder.

9. The method of forming a sandwich structure of claim 8 wherein the conductive geometry is comprised of a liquid conductive material and is contained in one of a cavity, tube and capsule to define its shape.

10. The method of forming a sandwich structure of claim 8 wherein the first dielectric substrate is comprised of a material having a relative dielectric constant greater than 2 and a loss tangent less than 0.1.